package session

import (
	"context"
	"database/sql"
	"errors"
	"sync"
	"testing"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/capability/restrict"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/channel/adapter"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/db"
)

// newTestManager opens a private in-memory SQLite handle and builds a manager
// over it. Each caller gets an isolated, non-shared database so parallel tests
// never contend.
func newTestManager(t *testing.T) (*SessionManager, *sql.DB) {
	t.Helper()
	ctx := context.Background()
	handle, err := db.Open(ctx, ":memory:", nil)
	if err != nil {
		t.Fatalf("db.Open(:memory:) = %v", err)
	}
	t.Cleanup(func() { _ = handle.Close() })

	m, err := New(ctx, handle, nil)
	if err != nil {
		t.Fatalf("New() = %v", err)
	}
	return m, handle
}

func TestGetOrCreateCreatesAndReuses(t *testing.T) {
	t.Parallel()

	m, _ := newTestManager(t)
	ctx := context.Background()
	msg := directMsg("o-100")

	first, err := m.GetOrCreate(ctx, msg, testOwner())
	if err != nil {
		t.Fatalf("GetOrCreate() = %v", err)
	}
	if first.SessionID == "" {
		t.Fatal("first SessionID empty")
	}
	if !first.Owner || !first.MemWritable {
		t.Fatalf("owner session Owner=%v MemWritable=%v, want true/true", first.Owner, first.MemWritable)
	}

	second, err := m.GetOrCreate(ctx, msg, testOwner())
	if err != nil {
		t.Fatalf("second GetOrCreate() = %v", err)
	}
	if second.SessionID != first.SessionID {
		t.Errorf("SessionID changed across calls: %q != %q", first.SessionID, second.SessionID)
	}
	if second.ChannelID != first.ChannelID {
		t.Errorf("ChannelID changed: %q != %q", first.ChannelID, second.ChannelID)
	}
}

func TestGetOrCreateDifferentChannelsDiffer(t *testing.T) {
	t.Parallel()

	m, _ := newTestManager(t)
	ctx := context.Background()

	s1, err := m.GetOrCreate(ctx, directMsg("o-100"), testOwner())
	if err != nil {
		t.Fatalf("GetOrCreate(sender1) = %v", err)
	}
	s2, err := m.GetOrCreate(ctx, directMsg("o-100"), testOwner())
	if err != nil {
		t.Fatalf("GetOrCreate(sender2) = %v", err)
	}
	// Same real account maps to the same session, so the channel id must be the
	// same; a different account must differ.
	s3, err := m.GetOrCreate(ctx, directMsg("stranger-1"), testOwner())
	if err != nil {
		t.Fatalf("GetOrCreate(stranger) = %v", err)
	}
	if s1.SessionID != s2.SessionID {
		t.Error("same account produced different sessions")
	}
	if s3.SessionID == s1.SessionID {
		t.Error("different account collided onto the same session")
	}
}

func TestGetOrCreateGroupIsolation(t *testing.T) {
	t.Parallel()

	m, _ := newTestManager(t)
	ctx := context.Background()

	// Owner speaking in a group: isolated context, memory read-only.
	sess, err := m.GetOrCreate(ctx, groupMsg("o-100"), testOwner())
	if err != nil {
		t.Fatalf("GetOrCreate(owner group) = %v", err)
	}
	if !sess.IsGroup {
		t.Error("group message not flagged IsGroup")
	}
	if !sess.Owner {
		t.Error("owner in group should still be Owner")
	}
	if sess.MemWritable {
		t.Error("group session must be read-only (MemWritable=false) even for owner")
	}
	if got := sess.Env(); got != restrict.ActorGroupMember {
		t.Errorf("Env() = %q, want group_member", got)
	}
}

func TestGetOrCreateStrangerIsolation(t *testing.T) {
	t.Parallel()

	m, _ := newTestManager(t)
	ctx := context.Background()

	sess, err := m.GetOrCreate(ctx, directMsg("stranger-1"), testOwner())
	if err != nil {
		t.Fatalf("GetOrCreate(stranger) = %v", err)
	}
	if sess.Owner {
		t.Error("stranger marked Owner")
	}
	if sess.MemWritable {
		t.Error("stranger session must be read-only (MemWritable=false)")
	}
	if sess.IsGroup {
		t.Error("stranger direct message marked IsGroup")
	}
}

func TestGetOrCreatePersistenceAcrossManagers(t *testing.T) {
	t.Parallel()

	ctx := context.Background()
	handle, err := db.Open(ctx, ":memory:", nil)
	if err != nil {
		t.Fatalf("db.Open = %v", err)
	}
	t.Cleanup(func() { _ = handle.Close() })

	m1, err := New(ctx, handle, nil)
	if err != nil {
		t.Fatalf("New#1 = %v", err)
	}
	first, err := m1.GetOrCreate(ctx, directMsg("o-100"), testOwner())
	if err != nil {
		t.Fatalf("m1.GetOrCreate = %v", err)
	}

	// A brand-new manager over the same database must recover the same binding.
	m2, err := New(ctx, handle, nil)
	if err != nil {
		t.Fatalf("New#2 = %v", err)
	}
	second, err := m2.GetOrCreate(ctx, directMsg("o-100"), testOwner())
	if err != nil {
		t.Fatalf("m2.GetOrCreate = %v", err)
	}
	if second.SessionID != first.SessionID {
		t.Errorf("session binding lost across managers: %q != %q", first.SessionID, second.SessionID)
	}
}

func TestGetOrCreateConcurrent(t *testing.T) {
	t.Parallel()

	m, _ := newTestManager(t)
	ctx := context.Background()
	msg := directMsg("o-100")

	const n = 20
	ids := make([]string, n)
	errs := make([]error, n)
	var wg sync.WaitGroup
	wg.Add(n)
	for i := 0; i < n; i++ {
		i := i
		go func() {
			defer wg.Done()
			sess, err := m.GetOrCreate(ctx, msg, testOwner())
			if err != nil {
				errs[i] = err
				return
			}
			ids[i] = sess.SessionID
		}()
	}
	wg.Wait()

	for i := 0; i < n; i++ {
		if errs[i] != nil {
			t.Fatalf("goroutine %d: GetOrCreate = %v", i, errs[i])
		}
		if ids[i] == "" {
			t.Fatalf("goroutine %d produced empty session id", i)
		}
		if ids[i] != ids[0] {
			t.Errorf("goroutine %d session id %q != %q", i, ids[i], ids[0])
		}
	}
}

func TestList(t *testing.T) {
	t.Parallel()

	m, _ := newTestManager(t)
	ctx := context.Background()

	if _, err := m.GetOrCreate(ctx, directMsg("o-100"), testOwner()); err != nil {
		t.Fatalf("GetOrCreate(owner): %v", err)
	}
	if _, err := m.GetOrCreate(ctx, directMsg("stranger-1"), testOwner()); err != nil {
		t.Fatalf("GetOrCreate(stranger): %v", err)
	}
	if _, err := m.GetOrCreate(ctx, groupMsg("g-member-1"), testOwner()); err != nil {
		t.Fatalf("GetOrCreate(group): %v", err)
	}

	got, err := m.List(ctx)
	if err != nil {
		t.Fatalf("List: %v", err)
	}
	if len(got) != 3 {
		t.Fatalf("List = %d sessions, want 3", len(got))
	}
	var owner, stranger, group bool
	for _, s := range got {
		switch s.ChannelID {
		case "direct-o-100":
			if !s.Owner || !s.MemWritable || s.IsGroup {
				t.Errorf("owner session flags = %+v, want owner/writable/not-group", s)
			}
			owner = true
		case "direct-stranger-1":
			if s.Owner || s.MemWritable || s.IsGroup {
				t.Errorf("stranger session flags = %+v, want non-owner/read-only/not-group", s)
			}
			stranger = true
		case groupChannelPrefix + "g1":
			if !s.IsGroup || s.MemWritable {
				t.Errorf("group session flags = %+v, want group/read-only", s)
			}
			group = true
		}
	}
	if !owner || !stranger || !group {
		t.Fatalf("missing sessions: owner=%v stranger=%v group=%v", owner, stranger, group)
	}
}

func TestListRecoveredFromTable(t *testing.T) {
	t.Parallel()

	ctx := context.Background()
	handle, err := db.Open(ctx, ":memory:", nil)
	if err != nil {
		t.Fatalf("db.Open = %v", err)
	}
	t.Cleanup(func() { _ = handle.Close() })

	m1, err := New(ctx, handle, nil)
	if err != nil {
		t.Fatalf("New#1 = %v", err)
	}
	if _, err := m1.GetOrCreate(ctx, directMsg("o-100"), testOwner()); err != nil {
		t.Fatalf("m1.GetOrCreate = %v", err)
	}

	// A brand-new manager over the same DB has an empty cache: List must
	// reconstruct the session from the backing table (cross-restart path).
	m2, err := New(ctx, handle, nil)
	if err != nil {
		t.Fatalf("New#2 = %v", err)
	}
	got, err := m2.List(ctx)
	if err != nil {
		t.Fatalf("List = %v", err)
	}
	if len(got) != 1 {
		t.Fatalf("List = %d sessions, want 1", len(got))
	}
	s := got[0]
	if s.ChannelID != "direct-o-100" || s.SessionID == "" {
		t.Fatalf("recovered session = %+v, want direct-o-100", s)
	}
	if !s.Owner || !s.MemWritable {
		t.Errorf("recovered owner flags = %+v, want owner/writable", s)
	}
}

func TestGetOrCreateInvalidChannel(t *testing.T) {
	t.Parallel()

	m, _ := newTestManager(t)
	ctx := context.Background()

	msg := adapter.UnifiedMessage{
		Platform:    "qq",
		ChannelType: adapter.ChannelDirect,
	}
	_, err := m.GetOrCreate(ctx, msg, testOwner())
	if !errors.Is(err, ErrInvalidChannel) {
		t.Fatalf("GetOrCreate(invalid) error = %v, want ErrInvalidChannel", err)
	}
}

func TestNewRejectsNilDB(t *testing.T) {
	t.Parallel()

	if _, err := New(context.Background(), nil, nil); !errors.Is(err, ErrNilDB) {
		t.Fatalf("New(nil db) error = %v, want ErrNilDB", err)
	}
}

// insertSessionAt writes a channel_sessions row directly with a caller-supplied
// raw created_at/updated_at, standing in for a mapping written by past code.
func insertSessionAt(t *testing.T, handle *sql.DB, cid, at string) {
	t.Helper()
	if _, err := handle.ExecContext(context.Background(),
		`INSERT INTO channel_sessions (platform, channel_id, session_id, actor_role, created_at, updated_at)
		 VALUES ('qq', ?, ?, 'owner', ?, ?)`,
		cid, "sess-"+cid, at, at); err != nil {
		t.Fatalf("insert %s: %v", cid, err)
	}
}

// TestListNewestFirstDeterministic covers the ordering contract: three mappings
// written within the same coarse clock tick share one created_at, so only the
// rowid tiebreak can define their order. List is newest first, so the row
// inserted last (highest rowid) must come first. The cache is deliberately empty
// so List reads the persisted order instead of cached entries.
func TestListNewestFirstDeterministic(t *testing.T) {
	t.Parallel()

	m, handle := newTestManager(t)
	ctx := context.Background()

	const at = "2026-09-07T03:20:05.830000000Z"
	for _, cid := range []string{"direct-a", "direct-b", "direct-c"} {
		insertSessionAt(t, handle, cid, at)
	}

	got, err := m.List(ctx)
	if err != nil {
		t.Fatalf("List = %v", err)
	}
	want := []string{"direct-c", "direct-b", "direct-a"}
	if len(got) != len(want) {
		t.Fatalf("List = %d sessions, want %d", len(got), len(want))
	}
	for i, w := range want {
		if got[i].ChannelID != w {
			t.Errorf("got[%d].ChannelID = %q, want %q (rowid DESC tiebreak)", i, got[i].ChannelID, w)
		}
	}
}

// TestListNewestFirstByCreatedAt checks the created_at DESC half: the mapping
// with the latest fixed-width timestamp is listed first even though it was
// inserted first and therefore has the lowest rowid.
func TestListNewestFirstByCreatedAt(t *testing.T) {
	t.Parallel()

	m, handle := newTestManager(t)
	ctx := context.Background()

	insertSessionAt(t, handle, "direct-newest", "2026-09-07T03:20:05.830978900Z")
	insertSessionAt(t, handle, "direct-oldest", "2026-09-07T03:20:05.830000000Z")

	got, err := m.List(ctx)
	if err != nil {
		t.Fatalf("List = %v", err)
	}
	if len(got) != 2 {
		t.Fatalf("List = %d sessions, want 2", len(got))
	}
	if got[0].ChannelID != "direct-newest" || got[1].ChannelID != "direct-oldest" {
		t.Errorf("List order = [%q %q], want newest first", got[0].ChannelID, got[1].ChannelID)
	}
}

// TestPersistWritesFixedWidthTimestamps pins the write path: GetOrCreate must
// store created_at/updated_at with the fixed-width layout so channel_sessions
// text ordering matches time ordering. RFC3339Nano would drop trailing zeros
// and persist a variable-width value instead.
func TestPersistWritesFixedWidthTimestamps(t *testing.T) {
	t.Parallel()

	m, handle := newTestManager(t)
	ctx := context.Background()

	if _, err := m.GetOrCreate(ctx, directMsg("o-100"), testOwner()); err != nil {
		t.Fatalf("GetOrCreate = %v", err)
	}
	var created, updated string
	if err := handle.QueryRowContext(ctx,
		`SELECT created_at, updated_at FROM channel_sessions WHERE channel_id = ?`,
		"direct-o-100").Scan(&created, &updated); err != nil {
		t.Fatalf("read stored timestamps: %v", err)
	}
	if len(created) != sessionTimeLen || len(updated) != sessionTimeLen {
		t.Errorf("stored timestamps = %q/%q (%d/%d bytes), want fixed width %d",
			created, updated, len(created), len(updated), sessionTimeLen)
	}
	if created != updated {
		t.Errorf("created_at %q != updated_at %q, want the same value on insert", created, updated)
	}
}